The aim of this paper is to analyse some aspects of the psychiatric and medical-social discourse on the relationship between childhood and insanity in Spain at the end of nineteenth century and during the first third of the twentieth century. We study the principal theories about degenerate children (delinquent childhood and anormal childhood) based on two of the most paradigmatic works of the Spanish medical literature: Estudio medico-social del nino golfo by Jose Sanchis Banus and Los ninos mentalmente anormales by Gonzalo Rodriguez Lafora.